Rogue RDP Connections

Since I noticed my ethernet connection performance as being saturated on my Windows 2012 R2 server,  I ran the netstat command & noticed alot of ip addresses having established connections to 3389. When looking further, I see that these ip addresses are from many different countries like korea, china, russia, turkey... What can I do to prevent these rogue connections? Are they authenticating to my server? Could there be an app on the server thats allowing this?
See only one example below:
  C:\Windows\system32>netstat -na | find "3389"
  TCP               LISTENING
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Luis MenaCommented:
Check your server event security logs and see if someone got authenticated. Is this server hosted locally or cloud? like azure. Check your firewall
What can I do to prevent these rogue connections?
Does the server need to have RDP enabled? It also sounds like you have it connected directly to your internet connection, versus being behind a firewall. The biggest question is do you need to have RDP open to the outside world? If not, then you need to make sure the rules of your firewall reflect that.

Multifactor authentication would be another way to go about it.  If only certain IPs from the outside have reason to connect, you could make your firewall rules reflect such.
Other options include implementing an RDP gateway that uses TLS, or configuring things in a manner that forces someone to connect to a VPN in order to have access to the network to RDP into the server.

Regardless of what you choose, I recommend putting a hardware firewall into place.

Are they authenticating to my server?
Better check your logs. At a minimum they're getting prompted to authenticate. I'd assume the worst, because they're going to keep trying to brute force their way in (assuming that they haven't already). Hope your passwords are complex! And you may want to change them while in the process of securing things.

Could there be an app on the server thats allowing this?
You have RDP enabled in a way where parties can connect from the outside. That's a server configuration thing, not an application.

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Dirk-Jan SmitsMission Critical EngineerCommented:
You could use
C:\> netstat -nao | find "3389"

to find the owning process id (ie: which process listens on port 3389)

and then try
C:\> tasklist  | findstr 1396

to find the name of PID 1396. In my case this is 'svchost.exe' which is normal for 'real' RDP connections.
In your case it might be a different process.

Rajul RajInformation Security OfficerCommented:
Use wireshark for  analyzing the network. and if you want to find out how they are connecting ., try to do a Vulnerability assessment on your server. And first thing first, If you dont want your RDP service for the server , you can disable it.
Natty GregIn Theory (IT)Commented:
First is to note IP addresses and block them via firewall rules.
Disconnect the sessions or try and see what files and resources they are accessing as admin u should be able to remote in without disturbing the user.
Assume full breach and follow your companies guide line in breach protocol.

I would immediately remove affected machines from service until cleaned or rebuild.
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Windows Server 2012

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